6748-84-1Relevant academic research and scientific papers
Site-Selective Acylation of Pyranosides with Oligopeptide Catalysts
Seitz, Alexander,Wende, Raffael C.,Roesner, Emily,Niedek, Dominik,Topp, Christopher,Colgan, Avene C.,McGarrigle, Eoghan M.,Schreiner, Peter R.
, p. 3907 - 3922 (2021/03/09)
Herein, we report the oligopeptide-catalyzed site-selective acylation of partially protected monosaccharides. We identified catalysts that invert site-selectivity compared to N-methylimidazole, which was used to determine the intrinsic reactivity, for 4,6
In Situ Switching of Site-Selectivity with Light in the Acetylation of Sugars with Azopeptide Catalysts
Eckhardt, André K.,Erb, Frederik R.,Herold, Dominik,Kind, Jonas,Niedek, Dominik,Schreiner, Peter R.,Seitz, Alexander,Thiele, Christina M.,Topp, Christopher,Wende, Raffael C.
supporting information, (2020/02/04)
We present a novel concept for the in situ control of site-selectivity of catalytic acetylations of partially protected sugars using light as external stimulus and oligopeptide catalysts equipped with an azobenzene moiety. The isomerizable azobenzene-peptide backbone defines the size and shape of the catalytic pocket, while the π-methyl-l-histidine (Pmh) moiety transfers the electrophile. Photoisomerization of the E- to the Z-azobenzene catalyst (monitored via NMR) with an LED (λ = 365 nm) drastically changes the chemical environment around the catalytically active Pmh moiety, so that the light-induced change in the catalyst shape alters site-selectivity. As a proof of principle, we employed (4,6-O-benzylidene)methyl-α-d-pyranosides, which provide a change in regioselectivity from 2:1 (E) to 1:5 (Z) for the monoacetylated products at room temperature. The validity of this new catalyst-design concept is further demonstrated with the regioselective acetylation of the natural product quercetin. In situ irradiation NMR spectroscopy was used to quantify photostationary states under continuous irradiation with UV light.
Acceleration and deceleration factors on the hydrolysis reaction of 4,6-O-benzylidene acetal group
Maki, Yuta,Kajihara, Yasuhiro,Nomura, Kota,Okamoto, Ryo,Izumi, Masayuki,Mizutani, Yasuhisa
, p. 15849 - 15856 (2021/01/18)
The benzylidene acetal group is one of the most important protecting groups not only in carbohydrate chemistry but also in general organic chemistry. In the case of 4,6-O-benzylidene glycosides, we previously found that the stereochemistry at 4-position altered the reaction rate constant for hydrolysis of benzylidene acetal group. However, a detail of the acceleration or deceleration factor was still unclear. In this work, the hydrolysis reaction of benzylidene acetal group was analyzed using the Arrhenius and Eyring plot to obtain individual parameters for glucosides (Glc), mannosides (Man), and galactosides (Gal). The Arrhenius and Eyring plot indicated that the pre-exponential factor (A) and ΔS? were critical for the smallest reaction rate constant of Gal among nonacetylated substrates. On the other hand, both Ea/ΔH? and A/ΔS? were influential for the smallest reaction rate constant of Gal among diacetylated substrates. All parameters obtained suggested that the rate constant for hydrolysis reaction was regulated by protonation and hydration steps along with solvation. The obtained parameters support wide use of benzylidene acetal group as orthogonal protection of cis- and trans-fused bicyclic systems through the fast hydrolysis of the trans-fused benzylidene acetal group.
Diisopropylethylamine-triggered, highly efficient, self-catalyzed regioselective acylation of carbohydrates and diols
Ren, Bo,Gan, Lu,Zhang, Li,Yan, Ningning,Dong, Hai
supporting information, p. 5591 - 5597 (2018/08/17)
A diisopropylethylamine (DIPEA)-triggered, self-catalyzed, regioselective acylation of carbohydrates and diols is presented. The hydroxyl groups can be acylated by the corresponding anhydride in MeCN in the presence of a catalytic amount of DIPEA. This method is comparatively green and mild as it uses less organic base compared with other selective acylation methods. Mechanistic studies indicate that DIPEA reacts with the anhydride to form a carboxylate ion, and then the carboxylate ion could catalyze the selective acylation through a dual H-bonding interaction.
Ceric ammonium nitrate/acetic anhydride: A tunable system for the O-acetylation and mononitration of diversely protected carbohydrates
Seepersaud, Mohindra,Seecharan, Savita,Lalgee, Lorale J.,Jalsa, Nigel Kevin
supporting information, p. 853 - 871 (2017/04/27)
Esterification of a wide range of partially protected carbohydrate derivatives was achieved using acetic anhydride and a catalytic amount of ceric ammonium nitrate (CAN). Compatibility with the commonly used protecting groups was demonstrated, with the es
Benzylidene Acetal Protecting Group as Carboxylic Acid Surrogate: Synthesis of Functionalized Uronic Acids and Sugar Amino Acids
Banerjee, Amit,Senthilkumar, Soundararasu,Baskaran, Sundarababu
supporting information, p. 902 - 906 (2016/01/16)
Direct oxidation of the 4,6-O-benzylidene acetal protecting group to C-6 carboxylic acid has been developed that provides an easy access to a wide range of biologically important and synthetically challenging uronic acid and sugar amino acid derivatives in good yields. The RuCl3-NaIO4-mediated oxidative cleavage method eliminates protection and deprotection steps and the reaction takes place under mild conditions. The dual role of the benzylidene acetal, as a protecting group and source of carboxylic acid, was exploited in the efficient synthesis of six-carbon sialic acid analogues and disaccharides bearing uronic acids, including glycosaminoglycan analogues.
Three Solvent-Free Catalytic Approaches to the Acetal Functionalization of Carbohydrates and Their Applicability to One-Pot Generation of Orthogonally Protected Building Blocks
Traboni, Serena,Bedini, Emiliano,Giordano, Maddalena,Iadonisi, Alfonso
, p. 3562 - 3572 (2016/01/25)
Three alternative protocols were developed to carry out the selective installation of acetal groups on carbohydrates and polyols under mildly acidic, solvent-free conditions. One protocol is based on a diol/aldehyde condensation at room temperature, with an acetolysis process serving for the activation of the carbonyl component. A second approach is based on an orthoester-mediated activation of the carbonyl component at high temperature. The third protocol is instead entailing a transacetalation mechanism. Combination of these methods allows a wide set of acetal-protected building blocks to be accessed in short times under very simple experimental conditions working under air. The scope of the latter two approaches was also extended to unusual one-pot synthetic sequences leading to concomitant Fischer glycosidation/acetal protection of reducing sugars.
2,4,6-Trichloro-1,3,5-triazine (TCT) mediated one-pot sequential functionalisation of glycosides for the generation of orthogonally protected monosaccharide building blocks
Tatina, Madhubabu,Yousuf, Syed Khalid,Mukherjee, Debaraj
, p. 5357 - 5360 (2012/07/30)
Orthogonally protected monosaccharide building blocks have been prepared using TCT in a one-pot multicomponent transformation. The process involves successive steps of arylidene acetalation, esterification and regioselective reductive acetal cleavage. High regioselectivity, scope for using a broad range of substrates, functional group tolerance, mild reaction conditions, easy handling process and wide application range are a few advantages of the current process.
Exciton chirality method in vibrational circular dichroism
Taniguchi, Tohru,Monde, Kenji
supporting information; scheme or table, p. 3695 - 3698 (2012/04/11)
The interaction of two IR chromophores yields a strong vibrational circular dichroism couplet whose sign reflects the absolute configuration of the molecule. We present a method to determine absolute configuration of a chiral molecule based on this couplet without need of theoretical calculation. Not only can this method analyze various molecules whose absolute configuration is difficult to determine by other spectroscopic methods, but also it can significantly enhance VCD signals.
Organosilicon-mediated regioselective acetylation of carbohydrates
Zhou, Yixuan,Ramstroem, Olof,Dong, Hai
supporting information; scheme or table, p. 5370 - 5372 (2012/06/18)
Organosilicon-mediated, regioselective acetylation of vicinal- and 1,3-diols is presented. Methyl trimethoxysilane or dimethyl dimethoxysilane was first used to form cyclic 1,3,2-dioxasilolane or 1,3,2-dioxasilinane intermediates, and subsequent acetate-c
